The basic physiology of vision has been understood for the best part of a century, but only in the last twenty years have scientists started to explore a second non-visual pathway by which the different colours we see affects our mind and body.

As well as cone cells in the retina which send information to the brain’s visual cortex, we also now know that certain cells in the eye respond to light by sending signals to the hypothalamus – an area of the brain which plays no part in forming the images we see.

So what does this mean? Well the hypothalamus is primarily responsible for the secretion of hormones, which in turn shape a number of our physical responses, for example body temperature, hunger, and the need for sleep.  In addition, the colour and wavelength of light transmitted to the hypothalamus can affect mood, alertness and impulsivity.

The Experience Design Group at the University of Leeds have been experimenting with different light colours to evaluate effect. They report a small increase in heart rate under blue light and a similar decrease under red light. Lead researcher Professor Stephen Westland points to Japan, where blue lights installed on train platforms in 2009 reduced the incidence of suicides by 74%, to support the notion that light can affect us in ways that go far beyond colour vision.

But he goes on to say that it is “becoming increasingly difficult to separate claims for the effects of colour that are supported by data, from those which are based on intuition or tradition”.  Hopefully Professor Westland’s work will add some much-needed evidence to the debate.

Sources:

1. The Conversation:
   Does colour really affect our mind and body? A professor of colour science explains.

2. Science Alert:
   Here's How Colours Really Affect Our Brain And Body, According to Science.